ACTG A5047: Evaluation of Potential Pharmacokinetic Interactions between Protease Inhibitors and Lipid-Lowering Agents. This study is being performed to try to determine which lipid lowering drugs can be administered safely and without pharmacokinetic interaction in patients taking HIV protease inhibitors, ritonavir + saquinavir. The administration of HIV protease inhibitors is associated with an increase in serum cholesterol and triglyceride. Sometimes these elevations are high enough that we need to intervene pharmacologically to lower these lipid levels. One of the groups of drugs that we use for this is the statins. These drugs are metabolized by the liver and utilize the enzymes that are inhibited by the HIV protease inhibitors. This can result in a potential interaction that result in very high levels of the statins which can cause damage to the muscles and liver. Not all of the statins are metabolized by the liver to the same extent. Thus, it is possible that one drug may have less interaction than another drug. The three most common statins in clinical use are pravastatin, simvastatin, and atorvastatin. In this study in HIV-negative volunteers, we will examine the effect of HIV protease inhibitor combinations, ritonavir + saquinavir, on the metabolism of the three statins. The blood levels of these statins will be evaluated before and after administration of HIV protease inhibitors. In addition, we will also examine whether pravastatin has any effect on nelfinavir, an HIV protease inhibitor, blood levels to be sure that the statins do not affect metabolism of HIV protease inhibitors. Our expectations are that this will not happen. This study should determine which of the three commonly used statins could be used safely with HIV protease inhibitors.